1. Field of the Invention
The present invention relates to an apparatus for adjusting tension of a saw chain wound and traveling around a guide bar of a chain saw.
2. Description of Related Art
In a chain saw, tension of a saw chain (hereinafter referred to as a chain) is adjusted by moving a guide bar in a longitudinal direction thereof against a sprocket that drives the chain to adjust a mutual distance.
As a chain tension adjusting apparatus of this kind, there is one that adjusts tension of the chain by moving the guide bar by a manual operation without using a tool.
Japanese Laid-open (Kokai) Patent Application Publication No. 2006-238876 discloses a chain tension adjusting apparatus described below. A slide nut attached to a guide bar is screwed with a screw member, and an adjusting wheel fixed to a rotating shaft of a gear meshing with a gear attached to an end portion of the screw member is rotated manually. Thus, the screw member is rotated, and the guide bar moves in an axial direction of the screw member integrally with the slide nut, to thereby adjust tension of a chain.
However, as described in Japanese Laid-open (Kokai) Patent Application Publication No. 2006-238876, in a case in which a rotating shaft of the adjusting wheel is disposed in parallel with the screw member, the adjusting wheel needs to be disposed outside an outside diameter of a nut member for fastening of the guide bar. Furthermore, when a radius of the adjusting wheel is enlarged for reducing an operating force, a space in which the adjusting wheel is disposed laterally from an attaching surface of the guide bar is enlarged to prevent interference with a traveling path of the saw chain in a chain saw main body, and thus, a width of the chain saw increases.
There is an apparatus in which an operating portion for chain tension adjustment is disposed at a part significantly away from a fastening portion of the guide bar to prevent interference with the traveling path of the saw chain and the like. However, such an apparatus has a complicated mechanism such as an increase in the number of gears for transmission of the operating force and cannot be reduced in size.